When plant cells are grown outside the plant in synthetic media, undifferentiated cell multiplication, called callus formation, is observed. The cells may also undergo plant cell differentiation with the development in culture of embryos or one or more portions of the plant, generally roots or shoots.
Differentiation of plant tissue culture is of importance in agriculture where rapid plant propagation of tissue culture is independent of seed availability and growing season. Plants produced from tissue culture have uniform characteristics and are free of virus.
Another application of plant tissue culture which depends on cell differentiation is the production of high value chemicals. Accordingly, a method for enhancing plant cell differentiation in cell tissue culture may also be used as an improved method for obtaining such chemical products.
The media on which plant tissue cultures are grown contain a carbohydrate component as the major nutrient. The carbohydrate usually comprises from 80 to 90% by weight of the solid constituents of the media. The preferred carbohydrates for this purpose have been sucrose or glucose. Occasionally, workers have used maltose, lactose, or other simple sugars.
We have now discovered, surprisingly, that if a proper combination of maltose and glucose is used as all or part of the carbohydrate component of the medium, improved cell differentiation of the cell tissue culture is observed. This results not only in enhanced production of roots and shoots, but also in the increased production of secondary chemicals by the cells.